Device for producing cam surfaces with merging sine-shaped portions



March 7, 1961 Filed Jan. 14, 1957 F. HECHT 2,973,696 DEVICE FOR PRODUCING CAM SURFACES WITH MERGING SINE-SI-LAPED PORTIONS 3 Sheets-Sheet 1 s FIGI 2H 1 T o 4 E U INVENTOR. FERDINAND HECHT BY W March 7, 1961 F. HECHT DEVICE FOR PRODUCING CAM SURFACES WITH MERGING SINE-SHAPED PORTIONS 5 Sheets-Sheet 2 Filed Jan. 14, 1957 INVENTOR. i FERDINAND HECHT II/I/l/l/l/IH [rt 28 March 7, 1961 F, HECHT 2,973,696

DEVICE FOR PRODUCING CAM SURFACES WITH MERGING SINE-SHAPED PORTIONS Filed Jan. 14, 1957 3 Sheets-Sheet 5 FIG. 4

f 4 I k INVENTOK FERDINANDv HECHT United States DEVICE FOR PRODUCING CAM SURFACES WITH MERGING. SINE-SHAPED PORTIONS The present invention relates to a method of and device for producing cams with portions connecting adjacent regions of the cam and which portions may be referred to as merging portions or transposition portions and which portions substantially precisely follow the law of the inclined sine graph.

It is a necessity that fast moving drives as they are customary in connection with packing machines, calculating machines and the like operate free from jerks and shocks. Frequently such movements are controlled by cam discs which work free from shocks and can easily be examined as to their properties it the merging portion of the effective cam area with the adjacent area follows a certain portion ofthe inclined sine graph.

The ascertainment of such graphs by calculating and drawing is time-consuming and inaccurate for the following reason. In order to be able to machine or cut out such curvature by means of a template and a cor- I responding tool, it .is necessary to define the graph by corresponding radii and tangents. However, it is evident that in spite of the utmost care in so dimensioning and designing the graph, such graph can never be precise because a merging or transposition portion of a cam which has a constant radius .defies the law of the sine movement.

A device is known according to which whendeveloping a circle along a straight line, a crank arm is caused to perform a rotative movement. The arrangement is such that a pivot is provided at the ends of the crank arm which pivot reciprocates a link or sliding member in the manner of a cross loop. However, this device is suitable only for producing an ordinary sine graph in the, Cartesian co-ordinate system.

Another method and device has been known by means of which sine and cosine functions with continuously varying speed length and amplitude can be produced as coordinates at a right angle with regard to each other. This known method consists in that the sine or cosine function a is graphically produced by transposition of an undamp- 2,973,696 Patent d Mar. 7, mar

ice

General arrangement The method according to the invention for producing and drawing the movement of a drive portion or drawing member in conformity with the law of the inclined sine line is characterized primarily in that the uniform straightline movement of a drive portion and the sinusoidal movement of a second drive part pertaining thereto are conveyed to a drive member carrying out the resulting movement in such a manner that the transposition up to half the oscillation length of the sine oscillation is effected in a subtractive manner and in the second oscillation half is effected in an additive manner.

In conformity with a development of the method according to the invention, a generating drive actuates a transmission link system leading to a drawing device in conformity with the law of the inclined sine graph. The

' movement of the link system results from the transposi tion or a uniform straight line movement and a straight line sinusoidal oscillatory movement. This movement is conveyed through an infinitely variable formrclosing stroke-changing member which is made effective and is acting upon a supporting arm guided along an arc.

The device according to the invention serves for draw- 1 ing cam discs and is characterized by a pivot which roened harmonic oscillation with'a rectilinear movement of constant speed which with regard to the direction of movement thereof extends in the plane of oscillation and perpendicular to the amplitude of oscillation. However,

it is not possible with these devices to draw circular cam discs which have precisely sine-shaped merging portions the inclined sine graph.

It is, therefore, an object of the present invention to provide a method of and device for producing cam areas or transition areas in conformity-with'the geometry of I orcam discs with merging or transition portions which precisely follow the law of the inclined sine graph.

It is another objectof this invention'to provide a dcvice'for drawing cams'of the above mentioned type which is simple in construction and' operation.

These and other objects and advantages of the invention will appearmore clearly'from v the following specification in connection with the-accompanying drawings, in which:

Fig.1 is augraphic representation of aninclinedsine r h; in t Qantas s m-r tates in clockwise direction and in a uniform manner upon the radius r equaling H 21r. The said pivot engages a slot of the cross loop in such a manner that it imposesupon said cross loop a sine oscillation with the amplitude H 2w. the same radius as the pitch diameter of a gear which rotates with the pivot in a synchronous manner and in the same direction. The gear meshes with a rack guided parallel to the oscillating direction of the cross loop whereby said last mentioned gear rack is uniformly moved in longitudinal direction thereof. According to the invention, the sinusoidal straight line oscillating movementof the cross loop, and the uniformly straight line movement of the rack together act upon a summary or accumulator I from the generating drive, consists of a link which con veys through a rack upon the gear segment of the supporting arm a component which corresponds to the tangent of the said angleQ The said link is pivotally connected to the output rail of the generating drive and is 'angularly adjustable in a form-closing manner. 5

The supporting arm is furthermore provided with a longitudinal slot for receiving and infinitely setting the radius of the stroke member guided along an are. i The supporting arm is angularly infinitely adjustable relative to the gear segment for setting the value of the inter;

mediate radius, and is also adjustablewith its centerof rotation by means of an adjusting rail in the direction in which the center-of the writing disc points] -In this way, the distance from the center of thecam disc up to the device is' sodesigned that the driveofthe writing disc during the production-ofthe sinusoidal cam transition According to the invention, the pivot is located on portion is conveyed by the spur gear of the generating drive through a further rack meshing with said gear to a link pivotally connected to said rack and angularly adjustable in an infinitely variable manner, said link being adapted to actin a form-closing manner. In this way, a rack perpendicular to said link and meshing with the spur gear of the writing disc, and consequently also the Writing disc are moved in the direction of the arrow by a component of movement of the spur gear of the generating drive which component corresponds to the angular adjustment of the link. The magnitude of this component of movement corresponds to the value T which in this way is likewise infinitely adjustable.

According to a further feature of the invention, the supporting arm provided for connection of the writing member may have associated therewith a chip-removing tool. Such a chip-removing tool may for instance be an end milling cutter which is driven by a separate motor, produces the movements of the supporting arm and cuts the desired curve directly into an appropriate material such as Plexiglas. Advantageously, the desired curve is cut at increased scale and is used as template for a copying milling machine which reduces the cam to original size.

In this way not only a more effective production of the cam disc is obtained since it can now be produced directly, but all errors are eliminated which are inherent to the transfer of the drawing prepared by said device upon the final cam disc or the master disc therefor for instance with the photochemical transmission with subsequent mechanical engraving.

The employment of Plexiglas or similar material as material for the template has the further advantage that the cutting force is low and that the chips will to a large extent adhere to the cam in view of the electrostatic effect occurring during the machining operation. At any rate it will be avoided that during the cutting operation steel chips will drop into the sensitive device. The control cams employed in fine mechanics are usually so small that his possible to produce the Plexiglas template on an enlarged scale. This brings about the two-fold advantage that the pressure of the pin of the reducing copying milling machine is low and that any deviations even though very small will practically vanish with'the reduction to original size.

Structural arrangement Referring now to the drawings in detail and Fig. 1

thereof in particular, this figure will explain the geometry of the inclined sine line in the Cartesian co-ordinate system. The abscissa of the co-ordinate system of Fig. 1 has plotted thereon the time with regard to a certain rotational speed. Thus, the distance OT corresponds to the angle T (Fig. 2) within which with the circular disc, the sineshaped transition occurs from a smaller to a larger radius or vice versa. H is the stroke, i.e. represents the difference between the said two radii. In order to assure that the transition will occur without a jerk and shock, the sine graph must be so located that it will contact the abscissa and the parallel thereto at a distance H where the turning point is located, i.e. where the radius of curvature is infinite. This is the case when the base line of the sine graph becomes the diagonal of the rectangle formed by H and T.

It is well-known that when H is given, the amplitude will be H/?.. While various possibilities exist, to plot this amplitude, the device according to the present invention is based on the Helling-Bestehorn method which consists in that the amplitude is plotted perpendicular to' the abscissa. This way of amplitude plotting and the graph obtained thereby has first of all. the advantageof simple algebraic relations. The equation of the inclined sine line according to Helling Bestehorn is:

H 27kt times sine As first derivation therefrom, the speed is obtained defined by the equation H H 21r I. y T minus times cosine T tunes a:

As second derivation there is obtained the acceleration defined by the equation 2 times sine & times a; T T

As will be evident from Fig. 1, also for the maxima particular simple values are obtained. The maximum speed is located at x= /2T, and the maximum of the acceleration is located at x= AT and %T.

Fig. 2 clearly shows that the transfer of this geometry of the inclined sine line from the Cartesian co-ordinate system to the polar system of the circular cam disc is made difiicult by various circumstances. First of all it is not the theoretical curve of the roller center which is to be produced but the equidistant thereto at the distance r as radius of the roller of the stroke member. This roller, however, is not guided linearly but along an arc whereby a further distortion of the graph is produced. Finally, the practical construction requires that all magnitudes obtainable from Fig. 2 are variable.

The particular advantage of the device according to the invention consists in that it automatically and precisely produces such cam discs, and furthermore in this way it eliminates the various sources of error which when producing such curves by calculation and graphic representation are based on the necessity that the various details obtainable from Fig. 2 have precisely and carey" =21r times fully to be taken into consideration.

Attention was directed above to the fact that the method of the amplitude plotting according to Helling- Bestehorn has the advantage that it is mathematically particularly simple. It is already for this reason that it is to be preferred because the mathematic simplicity influences the construction of the drive which produces the movement corresponding to the law of the inclined sine graph and which drive will henceforth be briefly designated as generating drive. It is a necessity that only a simple summary drive is involved which produces a movement according to which a uniform rectilinear movement has a sine oscillation transposed thereupon in such a manner that as clearly indicated in Fig. 1 this transposition will be subtractive up to T/2 and will be additive from T/ 2.

Fig. 3 diagrammatically illustrates the generating drive according to the invention. The pivot 1 uniformly rotating on the radius in clockwise direction engages the slot 2a of the cross loop 2 and imposes thereupon a sine oscillation with the amplitudeH/Zw. synchronously with and in the same direction as the pivot 1, a spur gear 3 is rotated the pitch diameter of which corresponds to the radius of the path of the pivot 1. The gear 3 drives the rack 4 in the direction of the arrow Z, which rack is guided parallel to the direction of oscillation of the cross loop 2.

After the pivot 1 and thus also after the gear 3 has performed a complete revolution, the cross loop 2 has carried out a complete sine oscillation with the amplitude 21:, While the rack 4 has carried out a uniform movement in the direction of the arrow Z amounting to Both movements are conveyed to the summary or accumulator wheel 5 so that the output rod 6 connected thereto will move in the direction of the arrow Y in the manner prescribed by the graph illustrated in Fig. 1. It would be possible already by means of this drive to 4 variable manner.

5 draw such graph in the linear system. To this end, it would be merely necessary to connect the free end of the rod 6 with a pen while a paper strip is passed uniformly below said pen perpendicular to the direction of movement of therod 6 in the direction of the arrow Y.

However, Fig. 2 clearly indicates thatthe device must do considerably more if it is to be suitablefor the described purpose. The problem involved is not merely to draw the graph in the polar system but also to ascertain the equidistant pertaining to the stroke roller with the radius r. Furthermore, the said stroke roller does not move along a straight line but along an arc, and finally all magnitudes obtainable from Fig. 2 namely the stroke H, the time angle T, the. magnitude A, i.e. the distance between the center of rotation of' the stroke member and the center of the cam disc, furthermore the radius L of the stroke member moved along an arc, the magnitude R indicating the mean value of the radii in the lowermost and uppermost position of the stroke member, and finally the radius r of the roller are variable and therefore it is necessary that they can be set in the device.

To this end, the device according to the invention and illustrated in its entirety in Fig. 4 is provided with a circular disc 7 upon which the sheet to be marked is to be fixed. The disc 7 is fixedly connected with the spur gear 8 meshing with the rack 9. The mesh between the rack 9 and the spur gears is necessary, however, only during the phase of the marking of the sine-shaped transition lineproper. The rack 9 is lifted out of mesh with gear 8 by a device 9a shown in the drawing, Fig. 4, when the concentric arc portions of the cam disc are being drawn. In connection therewith, also the writing disc 7 is freely rotatable and its angular position can be derived from the position of the pointer 10 relative to the disc 7.

For purposes of drawing the sine-shaped transition portion of the graph, thegenerating drive shown in Fig. 3 is rotated. in clockwise direction by 360. When said generating drive is so rotated, the spur gear, 3 moves the rack 11 in a uniform manner in the direction of the arrow W. Pivotally connected to said rack 11 is a link 12 the angular position of which can be read on a dial 13 while its angular position can be maintained by a screw 14 of any 'con'venient type, *jThe link 12 is provided with a longitudinal slot 12a which slot is engaged by the pivot; 15 of the rack 9. In this way, a component of movement corresponding to the adjusted angle will be conveyed through rack 9 to the writing disc 7. In other words the writing disc 7 will rotate by the angle T (Fig. 2) which angle can thus be set in an infinitely A similar link 16 is'piv'otally connected to a rail or bar 6shown in Fig. 3' on a larger scalethan in Fig. 4 whereby the component correspondingto the stroke H and pertaining to theoutput rail 6 moving according to the transposing law is conveyed to the rack 17. This rack 17 meshes with the gear segment 18 of the supporting arm 19. Also this mesh; between rack 17 and gear-segment 18 is interrupted prior to the marking of the concentric cam portions, while the supporting arm is held stationary.

The device further comprises a dial 20 for the stroke clamping screw 21 for variator 16 and also comprises a said variator 16.

In order to be able to set the other geometric: values, the

supporting arm 19 is angularly adjustable relative tothe gear segment 18 whereby the value R can be set. A clamping screw 22 is provided for securing the said-angular position or setting. Furthermore, the writingipen shown in Fig. Srnay be adjusted in the longitudinal opening or slot of, the supporting arm 19 whereby the value L (Fig. 2) can beset. The value r (Fig. 2) is represented by the-diameter of the writing pen. The length A can be set du'e tofthe fact that the center of rotation of the sup wa er i e a ai law ss s ee at:

. 6 justed in the direction toward the center of rotation of the writing disc 7.

The rail 23 is guided by two bolts, which bolts are fixed on the fundamental plate of the device. A clamping screw 23a allows the rail 23 to be filed in a desired position.

The writing pen is illustrated in detail in Fig. 5 and serves the purpose of drawing the equidistant to the graph upon which the center points of the rollers are located, in other words the writing pen draws the actual curve flank. The diameter of the writing pen equals 21'; in other words for each individual instance, a pen with corresponding diameter must be employed which fact, however, is of no economic importance in view of the considerably increased output of the device. This is all the more the case since when considering certain constructive possibilities it is possible to get by with a few standard diameters.

In order to design the device as simple as possible and to relieve the supporting arm from all avoidable forces, the writing pen is so designed that it will produce a precise and sharp-edged contour of the graph without rotating about its axis during the drawing operation. To this end, the writing pen is designed as hollow cylinder 24 at that side which faces the drawing sheet. The small sharp-edged ground edge of the hollowcylinder 24 confines a dish-shaped inner disc 25 whereby an annular gap is produced for delivering the India ink which is filled into the pen through the funnel 26 or the like.

Fig. 6, illustrates the arrangement of a miller instead of the supporting pen. To this end, the writing arm 19 has instead of a writing device such as a pen mounted thereon a miller 28 which preferably has the same diameter as the writing pen. The end milling cutter 28 is journalled in the spindle bearing 27 and together with the latter is adjustable in the longitudinal slot of arm 19 in conformity with the respective value L (see Fig. 2).

The drive of the cutter 28 is effected through the intervention of a motor not shown in the drawing. This motor is either stationarily pivotally connected above the arm 19 and connected with the cutter 28 through a flexible shaft 29 which follows the movements of the arm 19, or is likewise connected to the arm 19 and directly connected to the cutter. Inthis instance, the drive motor would carry out the movements of arm 19 in the same manner as the cutter 28.

It is, of course, understood that the present invention is, by no means, limited to the particular construction shown in the drawing but also comprises any modifications within the scope of the appended claims. Thus, for instance, the method and the device according to the invention may also be employed in connection with copying machines or the like. When producing curves of higher order, as for instance for the production of curves the differentiation of which and if desired still further difierentiations are continuous with regard to time, it is possible to replace the generating drive 3 by a cam template which is derived from the summary or accumulator wheel which in this instance is to be designed as sensing roller. In this instance, the device would still be further simplified.

What I claim is:

1. A device forproducing cams with transition surfaces following the law of the inclined sine graph, which comprises in combination: a first element, means for moving said element uniformly along a straight line, a second element, means for imposing upon said secondelement a straight line reciprocatoryv movement substantially parallel to the movement of said first element, transmission means drivingly connected to said first and second elements and arranged to superimpose the movements of said first and second elements upon each other to carry out a com- 7 t a movement followingthe law of the inclined sine line, a stroke-varying element, and a supporting arm movable along an arc',-said stroke-varying element being adjustable and being arranged to convey said composite movement to said supporting arm.

2. A device according to claim 1, which includes a working tool supported by said supporting arm and adapted to move along a line corresponding to said composite movement.

3. A device for producing cams with transition surfaces following the law of the inclined sine graph, which comprises in combination: a pivot arranged for uniform clockwise rotation along a circle having a radius of H/21r, where H is the stroke, a cross loop having a slot engaged by said pivot for imposing an inclined sine oscillation of the amplitude H/21r upon said cross loop, a

gear arranged for synchronous rotation with said pivot and having a pitch diameter equaling the diameter of the circle along which said pivot rotates, said gear being arranged for rotation in the same direction as said pivot, a rack, means for guiding said rack parallel to the direction of reciprocation of said cross loop, said gear meshing with said rack for moving the latter uniformly in longitudinal direction parallel to the direction of reciprocation of said cross loop, an accumulator wheel drivingly engaged by said cross loop and said rack for receiving a. combined movement composed of said inclined sine-shaped straight line reciprocating movement of said cross loop and said uniform straight line movement of said rack, an output rod linked to said accumulator Wheel, a marking element, and means operatively connected to said rod for actuating said marking element. v

4. A device according to claim 3, which in'clu'de's an additional rack, a gear segment adjustably connected to said marking element, an arm linked and angularly adjustable to said output rod, said additional rack being connected to said arm and movable thereby, said arm being operable to convey the component corresponding to the tangent of the adjusted angle of said arm relative to said output rod to said gear segment through said additional rack.

5. A device for producing cams with transition surfaces following the law of the inclined sine graph, which comprises in combination: a pivot arranged for uniform clockwise rotation along a circle having a radius of H/21r, where H is the stroke, a cross loop having a slot engaged by said pivot for imposing an inclined sine reciprocationof the amplitude H 21r upon said cross loop, a gear arrangedfor synchronous rotation with said pivot and having a pitchdiameter equaling the diameter of the circle along which said pivot rotates, said gear being arranged for rotation in the 'same direction as said pivot, a first rack, means 'for guiding said rack parallel to the direction of reciprocation of said cross loop, said gear meshing with said rack for moving the latter uniformly in longitudinal direction parallel to the direction of reciprocation of said cross loop, an accumulator Wheel dr'ivingly engaged by said cross loop and said rack for receiving a combined movement composed of saidinclined sine-shaped straight line, reciprocatory movement of said cross loop and said uniform straight line movement of said first rack, an output rod linked to said accurnuiator wheel and arranged for movement parallel to said rack, an and linked and angularly adjustable on said output rod, said arm being providedwithguiding means and being movable at an angle to said output rod, a second'rack movable by and along said guiding means, 'a slide rail extending and moving parallel to said second rack, a gear segment carried by said rail and meshing with saidseeond rack, a supporting 'arm for supporting asupporting element,- said marker arm being carried by said rail and being angularly adjustable relative to said gear segment, and a disc rotatably a 8 supported for receiving material to be marked, said rail and thus said supporting arm being movable selectively toward and away from the center of rotation of said disc.

6. A device according to claim 5, which includes a third rack meshing with said gear 'and movable thereby, an additional arm linked to and angularly adjustable relative tosaid third 'rack, means for maintaining said additional arm in its respective adjustable angular position relative to said third rack, an additional gear drivingly connected to said disc, and a fourth rack meshing with said additional gear and operatively connected to said additional arm so as to move in response to the movement of said additional arm.

7. A device for producing cams with transition surfaces following the law of the inclined sine graph, which comprises in combination: a pivot arranged for uniform clockwise rotation along a circle having a radius of H/Zar, where H is the stroke, a cross loop having a slot engaged by said pivot for imposing an inclined 'sine reciprocation of the amplitude H/Z'Ir upon said cross loop, a gear arranged for synchronous rotation with said pivot and having a pitch diameter equaling the diameter of the circle along which said pivot rotates, said gear being arranged for rotation in the same direction as said pivot, a first rack, means for guiding said rack parallel to the direction of reciprocation of said cross loop, said gear meshing with said rack for moving the latter uniformly in longitudinal direction, a'n accumulator wheel drivingly engaged by said cross loop and said rack for receiving a combined movement composed of said sine-shaped straight line reciprocatory movement of said cross loop and said uniform straight line movement of said first rack, an arm linked to said wheel and provided with a slot, said arm being angularly adjustable, a second rack having means extending into said slot for moving said rack in its longitudinal direction in response to the turning movement of said accumulator wheel, a gear segment rotatably journalled and meshing with said second rack, a supporting arm adjustably connected to said gear segment, a supporting arm carried by and angularly adjustable relative to said gear segment, and an annular writing pen carried by said supporting arm, said annular pen comprising a central member and a hollow cylindrical body surrounding said central member at spaced relationship thereto to form therewith an ink feeding passage, said hollow cylindrical body having its lower marginal portion formed into a sharp writing edge.

8. A device according to claim 7, which includes a rotatable support for receiving the material to be marked.

9. A device for producing cams with transition surfaces following the law of the inclined sine graph, which comprises in combination: a pivot arranged for uniform clockwise rotation along a circle having a radius of H 21r, where H is the stroke, a cross loop having a slot engaged by said pivot for imposing an inclined sine reciprocation of the amplitude 11/ 2'11- upon said cross loop, a gear arranged for synchronous rotation with said pivot and havinga pitch diameter equaling the diameter of the circle along which said pivot rotates, said gear being arranged for rotation-in the same direction as said pivot, a first rack, means for guiding said rack parallel to the direction of reciprocation of said cross loop, said gear meshing with said rack for moving the latter uniformly in longitudinal direction, an accumulator wheel drivin'gly engaged by said cross loop and said rack for receiving a combined movement composed of said inclined sine-shaped straight line reciprocatory movement of said cross loop and said uniform straight line movement of said first rack, an arm linked to said wheel and provided with a slot, said a'r'rn being angularly adjustable, a second rack having means extending into said slot for moving said second rack in its longitudinal direction in response to the turn ing movement of said accumulator wheel, a gear segment Iotatably journalled and meshing with said second rack, 21 supporting arm adjustably connected to said gear segment, at milling cutter carried by said supporting arm, and motor means drivingly connected to said milling cutter for rotating the same.

10. A device according to claim 9, in which the milling cutter in form of an end-milling cutter is journalled in a spindle bearing and together with the latter is adjustably supported by said supporting arm.

11. A device according to claim 10, which includes a universal joint shaft drivingly interconnecting said motor means and said milling cutter.

12. A device accordingto claim 10, in which said motor means for driving said milling cutter is connected to said supporting arm and directly connected to said cutter.

13. A device according to claim 2, in which said working tool is a writing pen.

References Cited in the file of this patent UNITED STATES PATENTS 2,507,547 Shepherd May 16, 1950 2,699,745 Ayres Jan. 18, 1955 FOREIGN PATENTS 1,031,222 France June 22, 1953 1,105,994 France July 13, 1955 875,571 Germany May 4, 1953 

